This invention relates to a valving arrangement, particularly adapted for an engine having a free-floating piston. Engines of this type offer numerous advantages, including unlimited bore to stroke ratio, the absence of side loading between the piston and the cylinder, and the elimination of heavy parts in the drive train. However, in such engines, smooth, uniform reciprocation is not inherent in the mechanical configuration. The motion of the free piston is governed only by the force of the working fluid and the resistance of the work being done. Therefore, valving is critical to assure that the working fluid will move the piston back and forth efficiently.
In accordance with this invention, the valve movement occurs as a result of the movement of the piston, automatically actuating the valves pneumatically as the piston approaches the end of its stroke. In one embodiment, the cylinder is constructed so as to have a chamber of reduced diameter at either end, forming extensions of the cylinder. Plungers project from the piston and are dimensioned to complementarily enter the chambers. The exhaust ports are within these chambers. Therefore, when a plunger of the piston enters one of the chambers, it cuts off the exhaust, trapping gas within the cylinder on the forward side of the piston. There is also a small fluid line connecting to either end of the cylinder. These two lines go to opposite ends of two valve assemblies. Within these assemblies are reciprocative floating valve members. As the piston approaches the end of its stroke, the pressure of the captured gas in the end of the cylinder is sensed in the small fluid lines, causing the valve members to move. In this way, the valve members are moved so as to appropriately open and close the inlet and exhaust to the cylinder so that the actuating fluid can force the piston back and forth through its stroke.